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Scientists hope to put breast cancers 'to sleep'

Scientists have suggested that it may one day be possible to push some breast cancers into a state of 'sleep' by targeting a gene involved in some aggressive forms of the disease.

Experts at the Garvan Institute of Medical Research in Sydney and the University of California San Francisco (UCSF) are in the early stages of research into Id1, a gene that is normally only switched on during the growth and development of embryos.

But scientists have discovered that this gene is often reactivated in many human tumours, and the San Francisco researchers found that it was frequently active in so-called 'oestrogen-receptor negative' breast cancers - some of the more aggressive and advanced forms of breast cancer.

These cancers lack oestrogen receptors, so do not respond to the drug tamoxifen.

Dr Alex Swarbrick, a scientist at the Garvan Institute, admitted that the team "happened to ask the right questions about the right gene".

"Up to that point, no-one else had asked whether or not Id1 actually contributed to the origin and behaviour of breast cancer."

Dr Swarbrick continued: "By artificially activating the Id1 protein in mouse mammary glands, we demonstrated that Id1 indeed contributes to cancer - and that mammary cancers with high levels of Id1 become very aggressive and highly metastatic.

"We also showed that if we genetically switch off the Id1 gene in an established tumour, those mice live much longer than mice with continual Id1 expression in their tumour. In fact about 40 per cent of them were cured and the tumours just shrank away."

The scientist noted that, surprisingly, the cells in the shrinking tumours did not actually die as expected but underwent 'senescence' - a term derived from the Latin verb meaning 'to grow old' - and lost their ability to divide.

Researchers hope that it may be possible to drive aggressive breast cancers into senescence, placing them in a state in which the tumour can no longer grow.

"You induce a terminal sleep, and then the immune system just gobbles them up," Dr Swarbrick suggested.

"Many cancers mutate the genes involved in cell death, so it's hard to kill them. Our results suggest that in the future if we can therapeutically target the genes controlling senescence, such as Id1, we can force these tumours to senesce."

The researchers' latest findings are published in the Proceedings of the National Academy of Sciences (PNAS).

Dr Joanna Peak, Cancer Research UK science information officer, said: "This research suggests that targeting the Id1 gene might one day help doctors to treat aggressive breast cancers that are resistant to current therapy.

"But this research was only carried out in mice, so the researchers need to show that these results hold true in humans. It will also be important to prove that switching cancer cells from a fast-growing state into a 'sleep mode' is as safe and effective as using drugs that directly kill them."

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